The Canadian CT Head Rule (CCHR) is a clinical decision-making tool designed for use in adult patients who have sustained a minor head injury. The CCHR helps clinicians determine which patients require a computed tomography (CT) scan to rule out clinically significant brain injuries, including fractures and intracranial hemorrhages. The rule is intended to reduce unnecessary radiation exposure and healthcare costs associated with CT scans. 

The CCHR applies to patients who have experienced a minor head injury, defined as a Glasgow Coma Scale (GCS) score of 13-15 after witnessed loss of consciousness, amnesia, or disorientation. It is not applicable to patients who are under 16 years old, have a seizure after injury, are on anticoagulant therapy, have a known brain tumor, or have a history of neurosurgery.

Canadian CT head rule (CCHR)

# Criteria
 # Exclusion criteria
A. Age < 16 years
B. Patient on blood thinners
C. Seizure after injury
# High risk criteria
D. GCS score < 15 at 2 hours after injury
E. Suspected open or depressed skull fracture
F. Sign of basilar skull fracture (hemotympanum, raccoon eyes, CSF otorrhea, CSF rhinorrhea, Battle's sign)
G. More than one episode of vomiting
H. Age >= 65 years
# Medium risk criteria
I. Amnesia of events extending >= 30 minutes before injury
J. "Dangerous" mechanism (pedestrian struck by motor vehicle, occupant ejected from a motor vehicle, or fall from > 3 feet or > 5 stairs)

# Conditions
- (A or B or C)
- (D or E or F or G or H or I or J)
- true